Koi pond plants need a little careful planting, to keep the water quality high. But nothing looks lovelier than colourful koi swimming around water lilies.
Koi ponds usually have fewer plants than other kinds of pond.
For one thing, with a koi pond, the colourful koi are the attraction, and too many plants will just make it harder to see them!
For another, water quality is important for koi, which means that the bottom of the pond needs to be clear to prevent debris accumulating and poisoning the water. So any koi pond plants need to be in their own containers.
Koi pond plants do offer one health benefit for your koi, though – they help provide shade, which is important to protect them from sunburn.
The safe approach to koi pond plants
As I was saying, koi pond plants need to be planted in containers, so that the soil can't get out into the water.
Take a basket, and line it with hessian or similar, so that water can flow in, but soil can't leak out. Then fill it with soil and earth (absolutely no fertilizer), and plant your plant. Place plenty of gravel and stones on the top to make sure that the koi don't kick up soil as they swim around.
Make sure you don't use fertilizer or insecticide, either in the soil you bed your koi pond plants in, or later on. This is a sure-fire way to poison your koi. Instead, trim away any infested areas of plants. It's a good idea, though, to wash you plants in something like potassium permanganate before planting, to get rid of any parasites. Make sure you rinse very thoroughly before you plant them!
In this photo, taken at the Hase-dera temple in Kamakura, Kanagawa, you can clearly see the ceramic pots which they use for the same purpose. Baskets are a a lot easier to handle, though!
Beautiful stone lantern, too, and note the way the shrubs behind it have been trimmed to look like a gentle hill.
(The photographer is jpellgen.)
Choosing koi pond plants
When choosing your plants, it's a good idea to continue the Japanese principle of seasonality, and make sure you have something of interest in each season.
Water lilies are the classic koi pond plant. Koi look absolutely gorgeous swimming in and out of sight under the leaves, and the flowers are beautiful too. Water lilies are visible on the surface from late spring to mid autumn. You can get lilies and lotuses in all kinds of colours, and for all kinds of climates.
Generally, one water lily will want about 10 square metres of your koi pond. They need between two and four feet of water depth, and at least a foot of soil in their planting basket.
Water lilies do need quite a lot of sun, so they're not a great option for very shaded koi ponds. Don't worry, though, if they don't flower in their first year – this is quite common.
Lotuses are another lovely pond plant.
Of course, your koi pond planting doesn't have to be limited to actual pond plants. You can have as many plants around the edge of your koi pond as you like. Irises are a classic choice for a Japanese pond, and provide a lovely splash of colour.
